The present invention relates generally to communication systems and specifically to multiplexing access lines of communication systems.
Congestion of transmission lines is a well known, and undesirable, situation in communication art. In order to solve congestion problems multiplexing (MUX)/demultiplexing (DEMUX) systems have successfully been incorporated to transmission lines.
FIG. 1A illustrates a block diagram which represent a transmission system 100, of prior art Transmission system 100 comprises two MUX/DEMUX units 102 and 104 and single line 114, preferably an optical fiber, which connects MUX/DEMUX units 102 and 104. Alternatively, line 114 may be a multiconductor line. Umits 102 and 104 are situated at two localities 106 and 108, remote from each other, where a plurality of POTS 110 and 112 are interfaced to units 102 and 104 respectively.
In accordance with the scheme illustrated in FIG. 1A, a plurality of communications from subscribers on lines 116, which enter MUX/DEMUX unit 102, converted to digital signals, multiplexed and routed, through line 114, to locality 108 by unit 102. Unit 104 demultiplexes the signals it receives from line 114, transforms the digital signals into electrical signals and redirects them through lines 118 towards their respective end communication devices (not shown) in locality 108.
The general scheme described above enables transmission system 100 to comprise only one single line connecting localities 106 and 108 and yet handle a plurality of communications.
FIG. 1B illustrates a variation of the prior art illustrated in FIG. 1A. A plurality of communications are routed by a switch board 120, through analog lines 122 to MUX/DEMUX unit 102, then to MUX/DEMUX unit 104 and then to end communication devices 124 in the described above in conjunction with FIG. 1A. Unit 104 is, optionaly power fed by a remote powers supply through lie 114, which in this case may be a multiconductor.
FIG. 1C illustrates a digital loop carrier (DLC) of prior art wherein a switchboard 126 sends a plurality of communication signals over a digital E1 line to a MUX/DEMUX unit 102. MUX/DEMUX unit 102 demultiplexes the plurality of signals it received one or more E1 lines 114 and redirects them towards respective subscribers in much the same way as described above.
The number of communications that can be handled by transmission lines pertaining to prior art described above, depends on the number of communications that each of the components, comprised in the lines, can support. Tie more powerful the components (i.e. components which can multiples/demultiplex greater number of signals) the greater number of communications that can be supported.
Transmission lines of the prior art do not allow their modular expansion. A transmission line of the prior art can be expanded by replacing the MUX/DEMUX components by more powerful MUX/DEMUX components.
It is an object of some preferred embodiments of the present invention, to provide a communication system (APIC) which has two stage multiplexing/demultiplexing capabilities.
In some preferred embodiments of this invention, a first multiplexing/demultiplexing stage (EU) is situated at, or in the vicinity of, a local exchange in a central office while a second, remote multiplexing/demultiplexing (RU) stage is situated at remote subscribers premises or in their vicinity. Preferably, a plurality of EU modules are comprised in a shelf so as to form a serial bus.
In some preferred embodiments of the present invention, a plurality of RU modules are interfaced to a single EU module. Preferably, an RU module supports 2 POTS (RU2 nodule). Alternatively, an RU module may support 10 POTS (RU10 module) or some number of POTS or other analog lines. Additionally, a single EU module may support RU2 and RU10 modules jointly. Alternatively, RU modules may support digital communication lines. Additionally, the RU modules may support POTS and digital communication lines jointly. Alternatively and/or additionally, RU modules generate preferably all necessary subscriber signals including current feed, ring, and/or metering.
In one aspect of the invention, the EU module comprised in some of preferred embodiments of the present invention, supports CAS protocols Additionally, the EU module may support newer CCS communication protocols like V5 communication protocol and/or ISDN-PRI protocol which enables these preferred embodiments to be connected to legacy and/or newer local exchanges. Additionally and preferably, the EU module comprises a power supply unit to remotely power the RU modules as well as the EU itself More preferably, the power supply unit comprised in the EU module comprises necessary protection and safety circuitry.
In one aspect of the invention, the APIC communication system does not require preliminary setup. Additionally, the APIC system. is preferably able to function independent of a central clock source. Preferably, the APIC communication system also allows for communication between any of the subscribers it serves, without connection to a central office.
There is thus provided, in accordance with a preferred embodiment of the invention, a communication system comprising:
a first multiplexing/demultiplexing stage positioned at a first locality and connected to a telephone interchange;
a plurality of second multiplexing/demunltiplexing stage positioned in a plurality of second localities apart from said first locality;
a communication channel such as a transmission line or a radio link which connects said first multiplexing/demultiplexing stage to each of said second multiplexing/demultiplexing stages; and
a plurality of subscribers lines connected to each of a plurality said second multiplexing/demultiplexing stages.
Preferably, the first stage is interfaced with said telephone exchange with a single digital interface.
Preferably, the digital interface comprises a plurality of logical lines wherein the total number of subscriber lines connected to said second multiplexing/demultiplexing stages is greater than said plurality of logical lines.
In a preferred embodiment of the invention, the subscribers include subscribers connected to said second stage by POTS lines. Alternatively or additionally the subscribers include subscribers connected to said second stage by ISDN lines.
There is further provided, in accordance with a preferred embodiment of the invention, communication apparatus, comprising:
a plurality of communication systems according to the invention;
a bus connecting said communications systems;
a control unit that mediates communication between said communication systems.
preferably, the switchboard connects a subscriber served by one of said second stages with a subscriber served by another of said second stages.
Preferably the communication apparatus includes means for grooming the switchboard.
There is further provided, in accordance with a preferred embodiment of the invention, a communication method comprising.
connecting a first multiplexing/demultiplexig stage to a telephone interchange;
connecting a plurality of second multiplexing/demultiplexing stage positioned in a plurality of second localities to each of said first multiplexing/demultiplexing stages;
connecting a plurality of subscribers to each of said second multiplexing/demultiplexing stages;
There is further provided, in accordance with a preferred embodiment of the invention, a communication method comprising:
connecting a plurality of first multiplexing/demultiplexing stages to a telephone interchange;
connecting a plurality of second multiplexing/demultiplexing stages positioned in a second locality to each of said first multiplexing/demultiplexing stage; and
connecting a plurality of subscribers to said second multiplexing/demultiplexing stage;
connecting said first stages via a bus; and
mediating between said first stages via said bus.
In a preferred embodiment of the invention, connecting said first stage comprises connecting said first stage to said telephone exchange with a single digital interface.
Preferably, the communication method comprises connecting a subscriber served by one of said second stages with a subscriber served by another of said second stages via said bus.
In a preferred embodiment of the invention, the subscribers include subscribers connected to said second stage by POTS lines. Alternatively or additionally,the subscribers include subscribers connected to said second stage by ISDN lines.